Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to circuit interrupters, such as, for example, aircraft or aerospace circuit breakers, that include a mechanism for sensing the status of the circuit interrupter.
Background Information
Aerospace power distribution units (PDUs), for example, generally include an enclosure, a number of input and output connectors, internal electrical bussing, electrical conductors, a number of electrical switching apparatus, such as contactors, circuit breakers, relays and the like, and/or fuses. More specifically, in aircraft or aerospace electrical systems, relatively small circuit breakers, commonly referred to as subminiature or aircraft circuit breakers, are often used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Typically, subminiature circuit breakers have provided protection against persistent overcurrents implemented by a latch triggered by a bimetal responsive to I2R heating resulting from the overcurrent. Aircraft circuit breakers also often serve as switches for turning equipment on and off, and are grouped together as part of a circuit protection module with the circuit breakers/switches being accessible on an outer panel of the enclosure within the aircraft.
It is often desirable to be able to automatically sense and indicate the position (open or closed) of a subminiature circuit breaker (so called “auxiliary monitoring”). Conventional circuit breaker position monitoring is achieved by adding a micro switch to a conventional circuit breaker. This implementation requires two additional small gauge wires to sense whether the micro switch is open or closed. The two additional wires require labor to install/remove and the small gauge wire is prone to environmental use and mechanical handling damage. Additionally, most applications for sensing position in this conventional fashion use “logic level” current, which often causes false misses/opens during the sensing process. As a result, it is often necessary to employ gold contacts in the micro switches to provide a more reliable logic level circuit. This, however, adds cost to the overall device.
Accordingly, there is room for improvement in circuit breakers, such as panel-mounted circuit breakers used aircraft or aerospace applications, which indicate status.